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M Nilsson

Publications and source records attributed to M Nilsson.

At least 235 records · Page 13Linked to original sources
PubMed1991

Integrity of the occluding barrier in high-resistant thyroid follicular epithelium in culture. II. Immediate protective effect of TSH on paracellular leakage induced by Ca2+ removal and cytochalasin B.

The acute influence of thyrotropin (TSH) on the Ca2+ and cytoskeleton dependence of the thyroid epithelial occluding barrier was investigated in porcine thyrocyte monolayers cultured on filter support. The barrier function was assayed by measurements of the transepithelial resistance (RTE) and the apicobasal flux (FTE) of radiotracers (125I-; [3H]inulin) as well as by morphological examination of junctions (fluorescein isothiocyanate-phalloidin labeling of F-actin; electron microscopy). Removal of extracellular Ca2+ (Ca2+e) by ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA) rapidly decreased RTE and increased FTE of both radiotracers. These changes were inhibited by TSH (1 mU/ml) given 6 min before Ca2+e removal. The inhibitory effect was total when Ca2+e was removed from the basal medium and partial when the cultures were totally deprived of Ca2+e. TSH added 10 min after basal depletion of Ca2+e partially reversed the changes in RTE and FTE. TSH also potentiated the recovery of RTE and FTE seen after readdition of Ca2+e. In contrast to Ca2+e-depleted cultures, the distribution of F-actin at the level of the junctional complex as well as the junctional ultrastructure were normal in cultures stimulated with TSH before depletion. TSH was also found to abolish the paracellular leakage induced by cytochalasin B (50 microM). TSH per se did not influence FTE of radiotracers. The observed effects of TSH were in all respects reproduced by forskolin (50 microM). In conclusion, acute stimulation with TSH protects the barrier function of porcine thyrocyte monolayers from the otherwise deleterious influence of Ca2+e-chelating and microfilament-disruptive agents. This effect of TSH is mediated by cyclic AMP. The data indicate that the integrity of the thyroid occluding barrier not only remains but is strengthened in TSH-stimulated cultures. The possible involvement of cell adhesion molecules in this response to TSH is discussed.

Actin Cytoskeleton↗
PubMed1991

Epidermal growth factor stimulates thyroid follicle neogenesis in collagen gel culture.

The mechanism involved in the neoformation of thyroid follicles is poorly understood. In the present study, whole porcine thyroid follicles were cultured as "miniorgans", embedded within collagen gels. Incubation was performed up to 4 days with or without EGF (10 ng/ml) and TSH (2 mU/ml). A single dose of 3H-thymidine was added at the start of the experiments in some cases. Light microscopy and autoradiography was performed. EGF induced a dramatic migration of follicles cells; these were seen to back out from the mother follicle and formed microfollicles with normal polarity including microvilli at the apical border. As evident from the analysis of 3H-thymidine incorporation, most microfollicles were comprised of newly divided cells. The results infer a new mechanism for the neoformation of follicles in the thyroid.

Animals↗
PubMed1991

Integrity of the occluding barrier in high-resistant thyroid follicular epithelium in culture. I. Dependence of extracellular Ca2+ is polarized.

The dependence of the thyroid occluding barrier on extracellular Ca2+ (Ca2+e) was studied in porcine thyrocyte monolayers resting on the collagen-coated porous filter of bicameral culture chambers. Ca2+ in the apical and basal media was selectively removed by ethylene glycol-bis(beta-amino-ethyl ether)N,N,N',N'-tetraacetic acid (EGTA), and the effect on occluding junction integrity was estimated by measuring the transepithelial electrical resistance (RTE) and the transepithelial flux (FTE) of 125I-, [3H]inulin and 125I-thyroglobulin. Experiments were also carried out to monitor the recovery of the occluding barrier after restitution of Ca2+e as well as to examine the effect of a second Ca2+ depletion period. Obtained data were correlated to changes in thyrocyte ultrastructure and distribution of filamentous actin as visualized by fluorescein isothiocyanate (FITC)-phalloidin. The thyrocyte monolayer developed RTE greater than 6000 ohms.cm2 after 6 to 8 days of culture. Total depletion of Ca2+e caused a rapid fall in RTE to about 50 ohms.cm2 after 10 min. Selective removal of Ca2+ in the basal medium induced a similar decline in RTE, which, however, was significantly retarded. Removal of apical Ca2+e alone was without effect on RTE. Corresponding responses were found in FTE experiments: the apicobasal transfer of radiotracers was unaltered after apical depletion, intermediary increased after basal depletion and maximally increased after total depletion of Ca2+e. Morphologically, monolayers lacking apical Ca2+e appeared normal except for shortening of microvilli at the apical plasma membrane. Removal of basal Ca2+e caused a focal dissociation of the adherens junction, which was most pronounced at the three-cell corners, leaving a slight dilation of the apical-most portion of the intercellular cleft. The adherent junction-associated actin bundle was partly retracted into the apical cytoplasm. The former occluding junction was distended and of reduced height at the sites of dissociated adherens junction. After total Ca2+ depletion, more severe alterations were found, i.e., contraction of cells and marked dilation of intercellular clefts. Readdition of Ca2+ to cultures depleted of basal Ca2+e for 10 min normalized RTE, FTE, and junctional morphology within 30 to 60 min. When a second period of basal depletion was introduced after recovery was obtained, the decrease in RTE and the retraction of the actin bundle occurred much more rapidly than during the first depletion. It is concluded that the thyroid occluding barrier depends on extracellular Ca2+ present only at the basal side of the occluding junction. Furthermore, this Ca2+ dependence seems to be spatially segregated along the lateral plasma membrane as well as along the circumference of the thyrocyte.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Decalcification by perfusion. A new method for rapid softening of temporal bones.

We describe a new technique, decalcification by perfusion, for the softening of bony tissue. The blood circulatory system was perfused in 16 rats via a cannula through the left heart ventricle with a fixative followed by New Decalc (an acidic demineralizer) for 30-240 minutes. Perfusion decalcification for 120 minutes softened all heads and middle ear specimens could be easily sampled and prepared for studies by both light and electron microscope. For comparison, a conventional immersion technique required 72 hours of decalcification to accomplish softening. The perfusion technique considerably reduced the time needed to decalcify the tissue and preserved the morphology better than did the immersion procedure.

Animals↗
PubMed1990

Loss of DNA-binding and new transcriptional trans-activation function in polyomavirus large T-antigen with mutation of zinc finger motif.

A putative zinc finger in polyomavirus large T-antigen was investigated. We were unable to demonstrate unequivocally a requirement for zinc in specific DNA-binding using the chelating agent 1, 10-phenanthroline. An involvement of the putative zinc finger in specific DNA-binding was nevertheless suggested by the properties of a mutant protein with a cys----ser replacement in the finger motif. Probably as a result of the defective DNA-binding, the mutant protein had lost its activity in initiation of viral DNA-replication and in negative regulation of viral early transcription. However, the trans-activation of the viral late promoter was normal. The analysis also revealed a previously unrecognized activity of large T-antigen. The mutant protein trans-activated the viral early promoter. In the wild-type protein this activity is probably concealed by the separate, negative regulatory function.

Amino Acid Sequence↗
PubMed1990

Transport of valproate and its effects on GABA uptake in astroglial primary culture.

The antiepileptic drug Na(+)-valproate (VPA) is a broadspectrum anticonvulsant. It has been proposed to be involved in the inhibitory mechanisms of GABA-ergic systems. In this study, transport of the drug and possible influence on the GABA uptake were investigated in primary astroglial cell cultures from newborn rat cerebral cortex. The results show a Na+ and K+ independent high affinity uptake for VPA, with km and Vmax not significantly different from those observed for the GABA uptake. In the presence of the drug, the Km-value of the GABA uptake increased. The GABA uptake inhibitors guvacine, (RS)-Cis-4-OH-nipecotic acid and 4,5,6,7-tetrahydroisoxazolo (4,5- c) pyridin-3-ol (THPO) did not influence upon the uptake of VPA, suggesting a transport mechanism for the drug, separated from the GABA uptake carrier.

Animals↗
PubMed1990

A viable mouse polyomavirus mutant without immortalizing or transforming activities.

The polyomavirus mutant, dl1041, has a 375-base pair deletion. It removes most of the sequences that are unique to rodent polyomaviruses and encodes part of the large and middle T-antigens. The mutant was conditionally viable, although both the immortalizing and transforming functions of the T-antigens produced by this mutant were found to be defective. However, the dl1041 mutant was found to be capable of DNA replication in rapidly growing mouse 3T6 cells. In contrast, dl1041 DNA synthesis could not be detected in serum-deprived mouse 3T3 cells. In these cells, the low efficiency of dl1041 DNA replication could be attributed to deficiencies in both large and middle T-antigen, suggesting a link between the mitogenic and oncogenic activities of these proteins. Transfection of growing mouse 3T6 cells with dl1041 DNA resulted in the formation of infectious virus, demonstrating that the dl1041 mutant is able to complete an infection cycle. The ability to activate the viral late promoter in trans was retained by the dl1041 mutant large T-antigen, suggesting that immortalization and trans-activation of the late promoter represent two distinct activities of the protein. An essential element of the immortalizing activity in the large T-antigen polypeptide chain appeared to be in a segment consisting of amino acid residues 136-184, since the dl1041 deletion abolished the activity and the 184 amino acid residue N-terminal dl1354 fragment of large T-antigen retained the activity.

Animals↗
PubMed1990

A method for determination of the absolute pulmonary bioavailability of inhaled drugs: terbutaline.

Terbutaline sulfate (4 X 0.250 mg) was given to 11 healthy volunteers by inhalation from a metered dose inhaler (MDI), with and without oral administration of a charcoal slurry. Before the inhalations, the adsorbing capacity of the charcoal slurry was tested. Deuterated terbutaline, 0.125 mg, was given intravenously at the same time as the test doses. The charcoal slurry adsorbed 97% of an oral dose. The oral contribution to the overall systemic bioavailability after inhalation, when charcoal was coadministered, could thus be neglected. After inhalation of terbutaline, 9.1% of the dose was deposited in the lungs and an additional 6.7% was systemically available via the oral route. The method presented measures the absolute pulmonary bioavailability after inhalation from a MDI. Since a deuterated analogue is given intravenously together with the inhalations, fewer subjects are needed to obtain reliable data.

Administration, Inhalation↗
PubMed1990

Empathy, experience of burnout and attitudes towards demented patients among nursing staff in geriatric care.

A non-anonymous questionnaire was distributed to all nursing staff (n = 557) including RNs, LPNs (psychiatric), LPNs (somatic) and nurses' aides, in one nursing home, one somatic long-term care clinic and one psychogeriatric clinic. Scales measuring empathy, burnout experience and attitudes towards demented patients were included in the questionnaire. The aim of the study was to compare levels of empathy, burnout experience and attitudes among different categories of nursing staff and to examine connections between empathy, burnout and attitudes. The nursing staff showed an overall figure of moderately well-developed empathy and the RNs showed the highest empathy. The RNs had a significantly lower degree of burnout compared to the nurses' aides and the LPNs. Of all respondents, 27.4% were assessed at risk from burnout. Overall, the staff showed a moderately positive attitude towards demented patients and the RNs were most positive. No linear correlation was found between empathy, burnout experience and attitudes. However, a weak negative correlation between burnout and empathy is in accordance with other authors who are suggesting that burnout experience leads to lower empathy in the nursing staff. The fact that the RNs showed the most positive attitudes towards demented patients and had the highest level of empathy compared to LPNs and nurses' aides could be related to lower degree of burnout assessed in the RNs. Qualitative and quantitative overload among the LPNs and nurses' aides connected to the growing number of demented patients in the institutions examined are discussed.

Adult↗
PubMed1990

Viable endospores of Thermoactinomyces vulgaris in lake sediments as indicators of agricultural history.

Bacteria of the genus Thermoactinomyces form endospores with an extreme longevity in natural habitats. We isolated Thermoactinomyces sacchari from 9,000-year-old varved (annually laminated) sediment; thus, T. sacchari is probably one of the oldest known living organisms. More importantly, we tested and verified the hypothesis that there is a relationship between concentrations of dormant, viable endospores of T. vulgaris in lake sediments and the extent of agriculture in the catchments of the lakes. In surface sediments, low concentrations were recorded in forest lakes and the concentrations increased with increasing areas of cultivated land around the lakes. In varved sediment cores from three lakes, we found a temporal relationship between records of T. vulgaris endospores and the pollen of plants indicating agriculture. Endospores were very rare in sediments deposited before agriculture, ca. 1100 A.D. From then to between 1300 and 1700 A.D., a period with restricted cultivation, low but more regular rates of accumulation of endospores were recorded. High endospore accumulation rates were found with the subsequent agricultural expansion. This investigation confirms suggestions that this bacterium could be used as a paleoindicator for agricultural activity and be complementary to pollen analyses. Viable bacteria in continuous records of lake sediments are also potential material for evolutionary studies.

Agriculture↗
PubMed1990

Effects of interleukin 1 alpha on porcine thyroid follicles in suspension culture.

Interleukin 1, a product primarily of activated macrophages, was found to exert both a stimulatory and an inhibitory effect on porcine thyroid follicles in suspension cultures. A stimulatory effect on [125I] iodide incorporation into protein (iodination) was seen in cultures exposed to human recombinant interleukin 1 alpha (20 micrograms/l) for 1 h and (0.1 or 10 micrograms/l) for 18 h, whereas an inhibitory effect on iodination of interleukin 1 (10 micrograms/l) was registered after pre-incubation for 42 h and significant upon stimulation with TSH (200 mU/l). Cyclic AMP levels were stimulated in cells exposed to interleukin 1, however, significantly only after 42 h of pre-incubation, whereas TSH-stimulated cAMP response was inhibited by interleukin 1 already after 18 h of pre-incubation. The lumen of interleukin 1 incubated follicles was highly dilated and surrounded by a flattened epithelium. There were, however, no morphological signs of follicle disintegration or cellular cytotoxicity in the cultures exposed to interleukin 1. The data suggest that interleukin 1 might have a modulating role on thyroid function in autoimmune thyroid diseases associated with activation of intrathyroidal macrophages.

Animals↗
PubMed1990

Iodide transport in primary cultured thyroid follicle cells: evidence of a TSH-regulated channel mediating iodide efflux selectively across the apical domain of the plasma membrane.

The transport of iodide was studied in porcine thyroid follicle cells cultured in bicameral chambers. The continuous layer of polarized follicle cells, joined by tight junctions, formed a diffusion barrier between the two compartments (apical and basal) of the culture chamber. Uptake and efflux of 125I- at either surface (apical and basolateral) of the cells were thus possible to determine. Protein binding of iodide was inhibited by methimazole (10(-3) M) in all experiments. Radioiodide was taken up by the cells from the basal medium in a thyroid-stimulating hormone (TSH)-dose dependent manner with a maximal cell/medium ratio of 125I- of about 50 in cultures prestimulated with 0.1 to 1 mU/ml for 2 days. This uptake was inhibited by perchlorate and ouabain. In contrast, 125I- was not taken up from the apical medium. In preloaded cells, iodide efflux was rapidly (within 1-2 min) and dose-dependently (0.1-10 mU/ml) stimulated by TSH. Bidirectional measurements revealed that TSH stimulated iodide efflux in apical direction, leaving efflux in basal direction unchanged. In experiments with continuous uptake of label from the basal compartment, the TSH-stimulated efflux in apical direction had a duration of 4 to 6 min and resulted in a reduction in the cellular content of radioiodide by up to 80%. Decreased levels of cellular 125I- remained for at least 15 min after TSH addition. From our observations we conclude that the TSH-regulated uptake and efflux of iodide take place at opposite surfaces of the porcine thyroid follicle cell. Acutely stimulated iodide efflux is not the result of an increased permeability for iodide in the entire plasma membrane but only in the apical domain of this membrane. This implicates the presence of an iodide channel mediating TSH-stimulated efflux across the apical plasma membrane of the follicle cell. The mechanism is suggested to facilitate a vectorial transport of iodide in apical direction, i.e., to the lumen of the intact follicle.

Animals↗
PubMed1990

Pharmacodynamics of beta-lactam antibiotics on gram-negative bacteria: initial killing, morphology and postantibiotic effect.

The aim of this study was to investigate the pharmacodynamics of beta-lactam antibiotics on Gram-negative bacteria by studying the in vitro postantibiotic effect (PAE), initial killing and morphology. The PAE of aztreonam, cefotaxime, ceftazidime, imipenem, mecillinam and piperacillin on Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Serratia marcescens was studied by use of bioluminescence assay of bacterial ATP. The strains were exposed for 2 h to the beta-lactam antibiotics which were then eliminated by 10(-4) dilution. With E. coli, spheroplasts were seen during incubation with cefotaxime, ceftazidime, imipenem and mecillinam and a long (greater than 1 h) PAE was noted. In contrast, aztreonam and piperacillin produced a short (less than or equal to 1 h) PAE. This was seen concomitantly with the production of filaments and weak initial killing.

Amdinocillin↗
PubMed1990

The postantibiotic effect of amikacin alone and in combination with piperacillin on gram-negative bacteria.

The in vitro postantibiotic effect (PAE) of amikacin was investigated using a bioluminescent assay of bacterial ATP. Two strains each of Escherichia coli, Pseudomonas aeruginosa and Serratia marcescens were exposed for one hour to different concentrations of amikacin. The aminoglycoside was removed by a 10(-3) dilution and regrowth of bacteria was followed at hourly intervals by monitoring bacterial ATP. The length of the PAE was concentration-dependent and was approximately four to six hours for the three strains at amikacin concentrations normally reached in serum during standard dosing. The PAE of amikacin in combination with 32 mg/l piperacillin on Ps. aeruginosa was also studied. These cultures were incubated with piperacillin for one hour. Thereafter different concentrations of amikacin 0.5-64 mg/l were added and the incubation then continued with the combinations for one more hour. The PAEs produced by the drugs in combination were longer than the sum of the individual effects of the drugs when they were used alone. Knowledge of synergistic PAE could have clinical implications for optimal dosing schedules during combination antimicrobial chemotherapy.

Amikacin↗
PubMed1989

Increased endocytosis and formation of multivesicular bodies in phorbol ester-stimulated human monoblastic U-937 cells.

The phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) is known to arrest mitotic activity and induce macrophage differentiation in the U-937 monoblastic cell line. The acute effect of TPA on ultrastructural morphology and endocytic activity of U-937 cells was studied. TPA induced within 15 min a marked enlargement of multivesicular bodies (MVBs), comprising both volume and number of inclusion vesicles (other organelles appeared unchanged). At this stage the MBVs frequently showed tubular cytoplasmic extensions. Inclusion vesicles accumulated in MBVs with prolonged incubation (60 min). Horseradish peroxidase (HRP) and cationized ferritin (CF) added to the medium were routed preferentially to MVBs in TPA-stimulated cells. In contrast to MVBs of unstimulated cells many of the TPA-induced MVBs showed a positive cytochemical reaction to acid phosphatase. The MVBs in cells incubated with ionomycin, a calcium ionophore, did not differ from those of unstimulated cells. Cellular uptake of 125I-HRP was increased five times the control values already after 5 min of TPA stimulation. The uptake increased further with prolonged incubation (60 min), but at a slower rate. Together these indicate a TPA-induced transfer by endocytosis of portions of the plasma membrane to the lysosomal system via MVBs. Consideration of MVBs as part of the receptor-mediated endocytic pathway suggests that this effect of TPA might involve down-regulation of cell-surface receptors. The possibility of MVBs as a proton-sequestrating compartment, responsible for the cytoplasmic alkalinization previously reported for TPA-stimulated U-937 monoblastic cells, is discussed.

Acid Phosphatase↗
PubMed1989

Effects of 2-guanidinoethane sulfonate on glutamate uptake in primary astroglial cultures from the rat cerebral cortex.

The competitive taurine uptake inhibitor 2-guanidinoethane sulfonate (GES) is frequently used to deplete cerebral pools of taurine. Previous work has revealed that extracellular glutamate increases during GES administration. In view of this, accumulation of glutamate in the absence or presence of 10 or 100 microM GES was measured in primary astroglial cultures from the rat cerebral cortex. At 100 microM, GES reduced Km as well as Vmax for glutamate uptake. A similar tendency was seen at 10 microM GES, but this was not statistically significant. The data suggest that GES is an uncompetitive inhibitor of reuptake of glutamate in astrocytes, which may underlie the previously noted GES-induced elevation of extracellular glutamate in vivo.

Animals↗